This invention relates to surgical apparatus and procedures in general, and more particularly to orthopedic prosthesis for restoring the hip joint.
Joint replacement surgery seeks to replace portions of a joint with prosthetic components so as to provide long-lasting function and pain-free mobility.
For example, in the case of a prosthetic total hip joint, the head of the femur is replaced with a prosthetic femoral stem component, and the socket of the acetabulum is replaced by a prosthetic acetabular cup component, whereby to provide a prosthetic total hip joint.
In the case of a prosthetic total knee joint, the top of the tibia is replaced by a prosthetic tibial component, and the bottom of the femur is replaced by a prosthetic femoral component, whereby to provide a prosthetic total knee joint.
The present invention is directed to orthopedic prostheses for restoring the hip joint and, more particularly, to improved prosthetic femoral stem components.
Prosthetic femoral stem components typically comprise a proximal section for seating in the proximal section of the resected femur and presenting a ball for seating in the acetabular socket, and a distal section for seating in the femur""s medullary canal so as to extend along the shaft of the femur.
It is, of course, important that the prosthetic femoral stem component make a proper fit with the surrounding bone. To this end, prosthetic femoral stem components are typically offered in ranges of different sizes in an effort to accommodate variations in patient anatomy. However, despite this, it has been found that it can be difficult to provide the correct prosthetic femoral stem component for patients. This is due to the wide variation in patient anatomies and to the practical limitations of hospital inventory. By way of example, where a femoral component is selected having a proximal section appropriately sized for the proximal section of the resected femur, the distal section of the prosthesis may not be appropriately sized for proper seating in the distal section of the femur. This can present serious problems for the patient, including problems relating to joint stability and pain.
On account of the foregoing, there has been substantial interest in forming prosthetic femoral stem components out of a plurality of separate elements, wherein each of the elements may be independently selected so as to most closely approximate patient anatomy, and wherein the separate elements may be assembled to one another in situ, using modular connections, so as to provide the best possible prosthetic femoral stem component for the patient.
Once deployed in the patient""s body, the prosthetic femoral stem component, and hence the modular connections securing the separate elements to one another, are subjected to axial, bending and torsional loads. While different types of modular connections are known in the art, no one modular connection is ideal for dealing with all three types of loads, i.e., axial, bending and torsional loads. By way of example, taper connections generally accommodate axial (i.e., compressive) loads well, but they generally do not accommodate bending and torsional loads particularly well. By way of further example, concentric cylinder connections generally accommodate bending loads well, but they generally do not accommodate axial and torsional loads particularly well.
As a result, one object of the present invention is to provide an improved modular connection for connecting together a plurality of separate elements so as to form a prosthetic femoral stem component.
Another object of the present invention is to provide an improved prosthetic femoral stem component.
And another object of the present invention is to provide an improved prosthetic total hip joint.
Still another object of the present invention is to provide an improved method for restoring a hip joint.
These and other objects are addressed by the provision and use of the present invention.
In one form of the invention, there is provided an improved modular connection for connecting together a plurality of separate elements so as to form a prosthetic femoral stem component, the improved modular connection comprising, in combination, a taper junction and an engaged-fit junction.
In another form of the invention, there is provided an improved prosthetic femoral stem component comprising a body element, a neck element and a stem element, with the body element, neck element and stem element being secured to one another with a modular connection, wherein the modular connection comprises, in combination, a taper junction and an engaged-fit junction.
In another form of the invention, there is provided an improved prosthetic total hip joint comprising a prosthetic femoral stem component and a prosthetic acetabular cup component, wherein the femoral stem component comprises a body element, a neck element and a stem element, with the body element, neck element and stem element being secured to one another with a modular connection, wherein the modular connection comprises, in combination, a taper junction and an engaged-fit junction.
In another form of the invention, there is provided an improved method for restoring a hip joint, wherein the method comprises the steps of: resecting the head of the femur and preparing the interior of the femur to receive a prosthetic femoral stem component; assembling a prosthetic femoral stem component comprising a body element, a neck element and a stem element by selecting appropriately sized elements and securing them together with a modular connection, wherein the modular connection comprises, in combination, a taper junction and an engaged-fit junction; and seating the prosthetic femoral stem component in the femur.